Compounds having 3-oxo-3,4-dihydro-2H-1,4-thiazine or 2-oxo-1,2,3,4-tetrahydropyrazine as a main skeleton, which are compounds having one double bond in their ring, have scarcely been studied. There were only reports concerning a study of introducing a phenyl group into the 5th-position of 3-oxo-3,4-dihydro-2H-1,4-thiazine derivatives (Japanese Laid-open Patent Publication No. 275869/1990), a study of synthesis of 2-oxo-1,2,3,4-tetrahydropyrazine derivatives as synthetic intermediates of 1,5-imino-3-benzoazocine derivatives aiming at analgesics or antitussives (Japanese Laid-open Patent Publication No. 35176/1983) and the like.
Much less, there has been no report relating to a study wherein various substituents are introduced into a nitrogen atom at the 4th-position of the 3-oxo-3,4-dihydro-2H-1,4-thiazine derivatives or into a nitrogen atom at the 1st-position of the 2-oxo-1,2,3,4-tetrahydropyrazine derivatives and their pharmaceutical utility is examined. In particular, compounds having carboxy-lower alkylene converted into amide, which are subjects of the present invention, have not been studied at all.
It is a very interesting subject to synthesize novel compounds having 3-oxo-3,4-dihydro-2H-1,4-thiazine or 2-oxo-1,2,3,4-tetrahydropyrazine as a main skeleton wherein various substituents are introduced into the nitrogen atom in their ring and to study their pharmaceutical utility.